The hippocampus, part of the limbic system, mediates learning and memory and is implicated in epilepsy. We are developing a multidisciplinary approach to study development and function of the excitatory and inhibitory neurons in the hippocampus. Using electroporation to transfect the hippocampal stem cells in utero, we will introduce fluorescent protein markers as well as mutated versions of the TrkB tyrosine kinase receptor into specific subregions of the hippocampal circuitry. The expression of these exogenous genes will be controlled temporally by placing them under the control of inducible gene promoters so that their expression coincides with particular phases of neuronal development. The functional effects of these molecular changes will be assessed by characterizing cell differentiation using immunochemical staining and by direct electrophysiogical measurements using patch clamp recording. These experiments will define a novel and rapid method for assessing the development, allocation and synaptic physiology of specific subpopulations of hippocampal neurons by introducing molecular changes in their germinal cells. This method will result in a technical advance for the study of hippocampal function and will be useful for understanding the underlying causes of abnormal synaptic transmission in diseases including epilepsy and mental retardation. PUBLIC HEALTH RELEVANCE:In this project we seek to develop methods for tracking the development and changing the gene expression of neurons in the hippocampus to enable rapid and cost-effective functional tests. In particular we will be assessing the role of the TrkB neurotrophin receptor in hippocampal neuronal migration and synaptic plasticity. To study both prenatal and postnatal effects of TrkB perturbation, we have engineered inducible plasmid constructs with which we can initiate expression of the transgene upon administration of tamoxifen. This work will enhance our ability to elucidate normal developmental mechanisms and allow rapid testing on causes of epilepsy and mental retardation.